Heat-shrinkable polyester film and package

Abstract

The invention provides a heat shrinkable polyester film which has (1) a hot-water heat shrinkage of not less than 55% and not more than 90% in a main shrinking direction of the film when dipped in hot water at 98° C.; (2) a hot-water heat shrinkage of not less than −5% and not more than 12% in a direction orthogonal to the main shrinking direction of the film when dipped in hot water at 98° C.; (3) a difference in specific heat capacity ΔCp between at a lower and a higher temperature than Tg of not less than 0.1 J / (g·° C.) and not more than 0.7 J / (g·° C.) when a reverse heat flow is measured with a temperature modulated DSC; and (4) a tensile breaking strength of not less than 70 MPa and not more than 150 MPa in the direction orthogonal to the main shrinking direction of the film.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application is the U.S. national phase of International Patent Application No. PCT / JP2015 / 056204, filed Mar. 3, 2015, which claims the benefit of Japanese Patent Application No. 2014-075842, filed on Apr. 1, 2014, and Japanese Patent Application No. 2015-005593, filed on Jan. 15, 2015, which are incorporated by reference in their entireties herein.TECHNICAL FIELD[0002]The present invention relates to a heat-shrinkable polyester film which is suitable for a label application and a package using the label.BACKGROUND ART[0003]Recently, in applications such as label package doubling as a protection of a glass bottle and a PET bottle etc. and display of articles, cap sealing and accumulation package, there have been widely used, as a shrink label, a polyester-based heat-shrinkable film which is high in heat resistance, easy to incinerate, and excellent in solvent resistance. The use amount of the polyester-based heat-shrinkable fil...

AI Technical Summary

Benefits of technology

[0020]Since the heat-shrinkable polyester film of the present invention is produced under the conditions that the mobile amorphous amount which contributes to shrinking is large and the mobile amorphous is not converted to rigid amorphous in the heat treatment process, a heat-shrinkable film having a higher heat shrinkage than conventional films can be provided.

[0021]Further, since the heat-shrinkable film is subjected to lengthwise-transverse biaxial drawing, the mechanical strength in the longitudinal direction orthogonal to the width direction is high. Therefore, the film can be very efficiently mounted to a container such as a bottle within a short time when used as a label for a PET bottle or the like, and the satisfactory finish with extremely reduced wrinkles and insufficient shrinkage can be exhibited when the film is shrunk by heat. Moreover, since the film strength is large, the processing properties at the time of printing processing and tubing processing are good.

[0022]Further, since the shrinkage stress of the film does not attenuate much and is kept high after 30 seconds from the initiation of shrinking, the film exhibits excellent followability even though a container is thermally expanded at the time of heating in the label mounting process, and the label is difficult to be slackened to thereby achieve a good appearance. In addition, the perforation opening property as a label is satisfactory, the label can be cleanly cut along the perforations from the start of tearing to the end of tearing when opened.

[0023]Moreover, since the heat-shrinkable polyester film of the present invention is a film produced by being biaxially drawn lengthwisely and transversely, the film can be very efficiently produced. Further, with regard to the heat-shrinkable polyester film of the present invention, the adhesive force at the time of bonding front and back surfaces (or two front or back surfaces) together by a solvent is extremely high, and the film can be suitably used for various cover labels and the like including a label for a PET bottle and the like.

[0024]A package packaged with a label obtained from the heat-shrinkable polyester film of the present invention has a beautiful appearance.

Problems solved by technology

The film subjected to drawing at a low ratio in the longitudinal direction and the film subjected to drawing only in the width direction have a drawback that the mechanical strength in the longitudinal direction is poor.

Moreover, when the film is subjected to drawing in the longitudinal direction in order to improve the mechanical strength in the longitudinal direction, the mechanical strength in the longitudinal direction increases, but the shrinkage in the longitudinal direction also increases, which in turn deteriorates shrinkage finishing properties.

On the other hand, when the shrinkage in the longitudinal direction is high, the length of the label in the longitudinal direction becomes short, which is contrary to the need to cover a major portion of a container with a label.

It is contradictory that while the mechanical strength in the longitudinal direction maintains high, the shrinkage in the longitudinal direction is reduced below zero, and this is difficult.

Further, when the shrinkage in the width direction is made higher, the shrinkage in the longitudinal direction also becomes higher, so that the film becomes inferior in shrinkage finishing properties.

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